Python 2 fix (string.isidentifier did not yet exist.)
Python 2 fix (string.isidentifier did not yet exist.)

ddalex/python-prompt-toolkit,jonathanslenders/python-prompt-toolkit,ALSchwalm/python-prompt-toolkit,niklasf/python-prompt-toolkit,Carreau/python-prompt-toolkit,Carreau/python-prompt-toolkit,jaseg/python-prompt-toolkit,amjith/python-prompt-toolkit,melund/python-prompt-toolkit